There exist several design constraints for satellites or other spacecraft which are contained within the payload fairing of a launch vehicle during their launch into space. Launching satellites and other spacecraft into space is expensive. Consequently, it is desirable to have satellite configurations of minimum weight and volume and that use the maximum amount of the volume within the fairing. It is also desirable for the configuration of a satellite to be adapted for housing more than one satellite within the fairing. However, housing multiple satellites within the fairing creates additional constraints on their design configuration. For example, when there are multiple satellites, each can be subjected to additional loads during the acceleration of the launch vehicle. This is especially true for the satellites located toward the bottom of the fairing if they must support the weight of the overlying satellites.
Several types of stacking arrangements have been proposed to accommodate the competing needs to maximize the utilization of space within the fairing and yet protect the satellites from loads experienced during launch. For example, King et al., U.S. Pat. No. 5,199,672 entitled "Method And Apparatus For Deploying A Satellite Network" discloses pallets disposed in a stacked configuration within the fairing. Each pallet mounts up to four satellites and includes a centrally located kick motor. The satellites in each layer are supported only by the pallet to which they are mounted thereby lessening the loads transferred to satellites which are lower in the stack. In addition, the central column of kick motors helps absorb the loads generated during acceleration thereby further protecting the satellites from these loads. However, this stacking arrangement suffers from the disadvantage that the mass and size of the satellites is limited by the mass and volume of the pallets. In addition, the central column of kick motors must be designed to withstand loads generated during launch.
StackSat is another example of stacked multiple spacecraft that have flown. In these, typically the lower spacecrafts suffer a substantial mass penalty because they must support the rest of the stack. The Ariane SPELDA and other vehicles have used a shell structure in which a lower satellite in the fairing is encased within a protective shell structure which supports the mass of an overlying satellite. However, the mass and volume of the shell diminishes that available for the satellites. Moreover, if the shell fails to open, the enclosed satellite cannot be deployed. An advantage of the shell is that it carries all the loads of the upper spacecraft so the structure of the lower one need not be strengthened.
The configuration of a satellite which is transported by a launch vehicle is further constrained by the need to provide energy to the satellite once it has been placed into orbit. Typically, arrays of solar panels are used to provide energy. In many previous satellite configurations, the arrays extend from the outer faces of the sidewalls of the satellite. When the satellite is stored within the fairing, the arrays are folded against the sides of the satellite to conserve space. The arrays are then deployed once the satellite is in orbit. Because the power generated by the solar panels is proportional to the surface area of the panels, satellites may require articulated panels which can be folded to fit within the fairing. The combined area of the articulated panels provides the required larger surface area when the panels are unfolded in orbit. However, increasing the number of articulations to provide a larger surface area also increases the cost of the satellite, complicates construction and testing of the satellite, and reduces the reliability of the panels during deployment and use.
It is therefore an object of this invention to provide a satellite configuration wherein several satellites of the same configuration can be stacked within the fairing of a launch vehicle.
Another object of this invention is to provide a stackable satellite configuration which maximizes the utilization of the space within the fairing.
A further object of this invention is to provide a stackable satellite configuration which protects the satellites from loads experienced during launching.
Another object of this invention is to provide a stackable satellite configuration in which the satellites have solar panels which provide a large surface area without excessive articulation.
Another object of this invention is to provide a stackable satellite configuration which protects the solar panels of the satellite during launching.
A further object of this invention is to provide a coupling device for coupling together satellites in a stack, wherein the coupling devices protect the satellites from loads experienced during launching.
Another object of this invention is to provide a coupling device for coupling together satellites in a stack, wherein the weight of the satellites is not substantially limited by the weight due to the coupling devices.
These and other objects will become apparent from the following description.